Ir Receiver

dda

IR receiver

Inisca Cristian

Coroiu Stefan

Content  Photodiode.  Phototransistor.

Photodiode

A photodiode is a type of photodetector capable of converting light into either current or voltage, depending upon the mode of operation . Photodiodes are similar to regular semiconductor diodes except that they may be either exposed or packaged with a window or optical fiber connection to allow light to reach the sensitive part of the device.

Photodiode

A photodiode is a PN junction or PIN structure. When a photon of sufficient energy strikes the diode, it excites an electron, thereby creating a mobile electron and a positively charged electron hole. If the absorption occurs in the junction's depletion region, or one diffusion length away from it, these carriers are swept from the junction by the built-in field of the depletion region. Thus holes move toward the anode, and electrons toward the cathode, and a photocurrent is produced .

Phototransistor Phototransistors also consist of a photodiode with internal gain. A phototransistor is in essence nothing more than a bipolar transistor that is encased in a transparent case so that light can reach the base-collector junction. The electrons that are generated by photons in the base-collector junction are injected into the base, and this photodiode current is amplified by the transistor's current gain. Note that while phototransistors have a higher responsivity for light they are not able to detect low levels of light any better than photodiodes. Phototransistors also have slower response times. A simple model of a phototransistor, would be a forward based LED (emitter–base) and a reverse based photodiode (base–collector) sharing an anode (base) in a single package such that 99% (αF%) of the light emitted by the led is absorbed by the photodiode. Each electron-hole recombination in the LED produces one photon and each photon absorbed by the photodiode produces one electron-hole pair.

IR LED Emitter An IR LED is made of gallium arsenide or aluminium gallium arsenide and emits light at a wavelenght of 760 nm or less.

IR filters are also used to obtain pure IR light .These filters are made of polysulfone but they can be made of many different materials.

IR Receiver IR Receiver needs to be in line of sight with the transmitter to efficiently transform light impulses into digital values.

The light emitted form the IR LED is modulated with a lens into a compact beam and than turned an and of concerning the message .